# Debug

Native VSCode debugger. Supports both GDB and LLDB.

## Installation

Press ctrl-p (cmd+p on OS X) and run `ext install webfreak.debug` in visual studio code and install GDB/LLDB. See `Usage` for details on how to set it up.

![Preview](images/preview.png)

## Usage

![Image with red circle around a gear and a red arrow pointing at GDB and LLDB](images/tutorial1.png)

Or if you already have an existing debugger in your project setup you can click "Create Configuration" or use the auto completion instead:

![Visual studio code debugger launch.json auto completion showing alternative way to create debuggers](images/tutorial1-alt.png)

Open your project and click the debug button in your sidebar. At the top right press
the little gear icon and select GDB or LLDB. It will automatically generate the configuration
you need.

*Note: for LLDB you need to have `lldb-mi` in your PATH*

If you are on OS X you can add `lldb-mi` to your path using
`ln -s /Applications/Xcode.app/Contents/Developer/usr/bin/lldb-mi /usr/local/bin/lldb-mi` if you have Xcode.

![Default config with a red circle around the target](images/tutorial2.png)

Now you need to change `target` to the application you want to debug relative
to the cwd. (Which is the workspace root by default)

Additionally you can set `terminal` if you want to run the program in a separate terminal with
support for input. On Windows set it to an empty string (`""`) to enable this feature. On linux
set it to an empty string (`""`) to use the default terminal emulator specified with `x-terminal-emulator`
or specify a custom one. Note that it must support the `-e` argument.

Before debugging you need to compile your application first, then you can run it using
the green start button in the debug sidebar. For this you could use the `preLaunchTask`
argument vscode allows you to do. Debugging multithreaded applications is currently not
implemented. Adding breakpoints while the program runs will not interrupt it immediately.
For that you need to pause & resume the program once first. However adding breakpoints
while its paused works as expected.

Extending variables is very limited as it does not support child values of variables.
Watching expressions works partially but the result does not get properly parsed and
it shows the raw output of the command. It will run `data-evaluate-expression`
to check for variables.

While running you will get a console where you can manually type GDB/LLDB commands or MI
commands prepended with a hyphen `-`. The console shows all output separated
in `stdout` for the application, `stderr` for errors and `log` for log messages.

Some exceptions/signals like segmentation faults will be catched and displayed but
it does not support for example most D exceptions.

Support exists for stopping at the entry point of the application.  This is controlled
through the `stopAtEntry` setting.  This value may be either a boolean or a string.  In
the case of a boolean value of `false` (the default), this setting is disabled.  In the
case of a boolean value of `true`, if this is a launch configuration and the debugger
supports the `start` (or `exec-run --start` MI feature, more specifically), than this
will be used to run to the entry point of the application.  Note that this appears to
work fine for GDB, but LLDB doesn't necessarily seem to adhere to this, even though it may
indicate that it supports this feature.  The alternative configuration option for the
`stopAtEntry` setting is to specify a string where the string represents the entry point
itself.  In this situation a temporary breakpoint will be set at the specified entry point
and a normal run will occur for a launch configuration.  This (setting a temporary
breakpoint) is also the behavior that occurs when the debugger does not support the
`start` feature and the `stopAtEntry` was set to `true`.  In that case the entry point will
default to "main".  Thus, the most portable way to use this configuration is to explicitly
specify the entry point of the application.  In the case of an attach configuration, similar
behavior will occur, however since there is no equivalent of the `start` command for
attaching, a boolean value of `true` for the `stopAtEntry` setting in a launch configuration
will automatically default to an entry point of "main", while a string value for this
setting will be interpreted as the entry point, causing a temporary breakpoint to be set at
that location prior to continuing execution.  Note that stopping at the entry point for the
attach configuration assumes that the entry point has not yet been entered at the time of
attach, otherwise this will have no affect.

### Attaching to existing processes

Attaching to existing processes currently only works by specifying the PID in the
`launch.json` and setting `request` to `"attach"`. You also need to specify the executable
path for the debugger to find the debug symbols.

```
"request": "attach",
"executable": "./bin/executable",
"target": "4285"
```

This will attach to PID 4285 which should already run. GDB will pause the program on entering and LLDB will keep it running.

### Using `gdbserver` for remote debugging (GDB only)

You can also connect to a gdbserver instance and debug using that. For that modify the
`launch.json` by setting `request` to `"attach"` and `remote` to `true` and specifing the
port and optionally hostname in `target`.

```
"request": "attach",
"executable": "./bin/executable",
"target": ":2345",
"cwd": "${workspaceRoot}",
"remote": true
```

This will attach to the running process managed by gdbserver on localhost:2345. You might
need to hit the start button in the debug bar at the top first to start the program.

Control over whether the debugger should continue executing on connect can be configured
by setting `stopAtConnect`.  The default value is `false` so that execution will continue
after connecting.

### Using ssh for debugging on remote

Debugging using ssh automatically converts all paths between client & server and also optionally
redirects X11 output from the server to the client.  
Simply add a `ssh` object in your `launch` request.

```
"request": "launch",
"target": "./executable",
"cwd": "${workspaceRoot}",
"ssh": {
	"forwardX11": true,
	"host": "192.168.178.57",
	"cwd": "/home/remoteUser/project/",
	"keyfile": "/path/to/.ssh/key", // OR
	"password": "password123",
	"user": "remoteUser",
	"x11host": "localhost",
	// x11port may also be specified as string containing only numbers (useful to use configuration variables)
	"x11port": 6000,
	// Optional, content will be executed on the SSH host before the debugger call.
	"bootstrap": "source /home/remoteUser/some-env"
}
```

`ssh.sourceFileMap` will be used to trim off local paths and map them to the server. This is
required for basically everything except watched variables or user commands to work.

For backward compatibility you can also use `cwd` and `ssh.cwd` for the mapping, this is only used
if the newer `ssh.sourceFileMap` is not configured.

For X11 forwarding to work you first need to enable it in your Display Manager and allow the
connections. To allow connections you can either add an entry for applications or run `xhost +`
in the console while you are debugging and turn it off again when you are done using `xhost -`.

Because some builds requires one or more environment files to be sourced before running any
command, you can use the `ssh.bootstrap` option to add some extra commands which will be prepended
to the debugger call (using `&&` to join both).

### Extra Debugger Arguments

Additional arguments can be supplied to the debugger if needed.  These will be added when
the debugger executable (e.g., gdb, lldb-mi, etc.) is launched.  Extra debugger arguments
are supplied via the `debugger_args` setting.  Note that the behavior of escaping these
options depends on the environment in which the debugger is started.  For non-SSH
debugging, the options are passed directly to the application and therefore no escaping is
necessary (other than what is necessary for the JSON configuration). However, as a result
of the options being passed directly to the application, care must be taken to place
switches and switch values as separate entities in `debugger_args`, if they would normally
be separated by a space.   For example, supplying the option and value
`-iex "set $foo = \"bar\""` would consist of the following `debugger_args`:
```json
"debugger_args" : ["-iex", "set $foo = \"bar\""]
```
If `=` is used to associate switches with their values, than the switch and value should
be placed together instead.  In fact, the following example shows 4 different ways in
which to specify the same switch and value, using both short and long format, as well as
switch values supplied as a separate parameter or supplied via the `=`:
- ```json
  "debugger_args" : ["-iex", "set $foo = \"bar\""]
  ```
- ```json
  "debugger_args" : ["-iex=set $foo = \"bar\""]
  ```
- ```json
  "debugger_args" : ["--init-eval-command", "set $foo = \"bar\""]
  ```
- ```json
  "debugger_args" : ["--init-eval-command=set $foo = \"bar\""]
  ```
Where escaping is really necessary is when running the debugger over SSH.  In this case,
the options are not passed directly to the application, but are instead combined with the
application name, joined together with any other options, and sent to the remote system to
be parsed and executed.  Thus, depending on the remote system, different escaping may be
necessary.  The following shows how the same command as above needs to be escaped
differently based on whether the remote system is a POSIX or a Windows system.
- SSH to Linux machine:
  ```json
  "debugger_args": ["-iex", "'set $foo = \"bar\"'"]
  ```
- SSH to Windows machine:
  ```json
  "debugger_args": ["-iex", "\"set $foo = \\\"bar\\\"\""]
  ```
You may need to experiment to find the correct escaping necessary for the command to be
sent to the debugger as you intended.

## [Issues](https://github.com/WebFreak001/code-debug)